The use of such tool cutter heads which are releasably mounted on a tool holder so as to be firmly secured thereto in such a manner as to minimize the danger of relative movement between the tool cutter head and the tool holder has been previously proposed. In this connection reference is made to Swiss Patent Specification No. 249,179, Swedish Patent Specification No. 40469, Japanese Utility Patent Application (Kokai) No. 52-165388 and U.S. Pat. No. 4,270,422. The latter document discloses the provision of a tool cutter head designed to have a cutter insert mounted thereon, the cutter head being designed to be clamped against a tool holder by means of a drawer which is axially moveable within the tool holder. For this purpose the tool cutter head is formed, at one end thereof with a recess having a restricted opening defined between a pair of flanges which project from and are formed integrally with the tool head. The drawbar is formed with an engaging head which projects out of that end of the tool holder opposite the one end of the tool cutter head and between a pair of abutment surfaces formed integrally with the tool holder. The engaging head is receivable in the recess with the projecting flanges bounding a neck portion of the drawbar, juxtaposed surfaces of the engaging head and the projecting flanges constituting respective cam surfaces such that displacement of the drawbar into the tool holder results in the clamping of the head against the tool holder including the outward displacement of the flanges against the abutment surfaces.
With this hitherto proposed tool cutter head the effectiveness of the clamping thereof against the tool holder and in consequence the degree of stability of the entire tool assembly depends on the effective displacement in order to achieve an effective contact of the projecting flanges against the abutment surfaces. With the flanges formed integrally with the tool head there is an inherent limit on the degree of elastic deformation which these flanges can bear under the influence of the displaced engaging head of the drawbar without fracturing or otherwise undergoing non-reversible deformation. Furthermore, should fracture or non-reversible deformation of the flanges occur, the entire tool head is rendered non-operational and must be entirely replaced.